Many situations call for drills and associated drill rigs for forming holes in drill resistant materials. Such materials may include heavy gauge metals or alloys. Additional problems are presented when a drilling application requires a portable drill rig capable of applying large amounts of drill pressure.
As only one example, many safes and secure storage containers are constructed of strong, heavy gauge metal. One or more locks, such as combination locks, are provided to secure the contents from access by unauthorized personnel. In the absence of the safe owner or other authorized personnel, or in the event that the lock malfunctions or the key or combination is lost or forgotten, locksmiths must be called upon to open the safe or container. Often, this involves drilling one or more holes in a wall or door of the structure so that the inner workings of the lock may be viewed by the locksmith. This may be accomplished with an appropriate viewing device, such as a borescope. Holes may be required for other access methods as well. Although safes and high security storage containers may be opened by force, this is typically not desirable because of the resulting damage. When small holes are instead used, for example, to view the various tumbler wheels of a combination lock, the safe or storage container may be opened with very little damage and, therefore, may be repaired and reused in many cases.
Drill rigs exist for allowing holes of the above described type to be formed in a safe or locked storage container. Examples may be found in U.S. Pat. Nos. 4,662,201; 4,865,493; and 4,978,257, each assigned to the assignee of the present invention. Areas still in need of improvement generally relate to the mechanism used for incrementally advancing the drill bit and the mechanism used for completely withdrawing the drill bit and the attached drill bit holding and advancing mechanism or quill, such as for drill bit replacement purposes. In this latter regard, in some of the highest security safes and containers, which are formed from extremely highly drill resistant and/or heavy gauge metals, it is not uncommon to break or wear out several drill bits during the course of forming one hole.
The drill rig disclosed in U.S. Pat. No. 4,978,257 is especially suitable for high security containers. This drill rig uses fine pitched external threads on a drill bit holding and advancing mechanism in the form of a barrel assembly to apply and maintain fine increments of axial pressure without substantial effort or fatigue on the part of the user. Depth of penetration may also be viewed in small increments. One drawback, however, is that the drill bit holding and advancing mechanism is not easily inserted and withdrawn from the frame structure associated with the rig. Rather, the user must generally thread the entire mechanism out of the frame structure to replace a drill bit. Moreover, this drill rig and other similar drill rigs use exposed, external threads to apply axial drilling pressure. These threads are therefore susceptible to receiving stray metal burrs and chips thrown out from the drilled hole. The burrs and chips may then interfere with the engaging threads and make withdrawal, insertion and axial adjustment of the mechanism more difficult or impossible.
U.S. Pat. No. 4,865,493 discloses one type of sliding connection for mounting a drill bit holding and advancing mechanism within a frame structure. However, this patent discloses a rack and pinion or drill press-type mechanism for applying axial drilling pressure. While this type of mechanism is adequate in some lighter duty situations, in many situations the advantages of applying incremental and maintained drilling pressure through the use of a threaded mechanism is desirable or even necessary. Such lever rigs or drill press style rigs cannot maintain the constant pressure that threaded rigs can maintain without increased operator effort and fatigue. Depth of penetration is also more difficult to ascertain.
It would therefore be desirable to provide a drill rig that allows an operator to incrementally adjust and maintain drill pressure, while minimizing effort and fatigue, and while preventing metal chips and burrs from interfering with the threaded members associated with the guide and allowing quick and easy insertion and withdrawal of the drill bit holding and advancing mechanism.